Photomask blank, method of manufacturing the same, photomask, and method of manufacturing the same

ABSTRACT

A photomask blank for use in the manufacture of a photomask adapted to be applied with exposure light having a wavelength of 200 nm or less has a thin film on a transparent substrate. The thin film is made of a material containing a transition metal, silicon, and carbon and comprising silicon carbide and/or a transition metal carbide.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Divisional of application Ser. No. 13/201,368 filed Oct. 12,2011 claiming priority based on International Application No.PCT/JP2010/051625 filed Feb. 4, 2010, which claims priority fromJapanese Patent Application No. 2009-030925, filed on Feb. 13, 2009, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This invention relates to a photomask blank and a photomask which areimproved in irradiation durability, and to methods of manufacturingthem. In particular, this invention relates to a photomask blank for usein the manufacture of a photomask to be suitably used in an exposureapparatus using exposure light having a short wavelength of 200 nm orless as an exposure light source, and to such a photomask and methods ofmanufacturing them.

BACKGROUND ART

Generally, fine pattern formation is carried out by the photolithographyin manufacturing processes of a semiconductor device. A number ofsubstrates called photomasks are normally used for this fine patternformation. The photomask comprises generally a transparent glasssubstrate having thereon a fine pattern made of a metal thin film or thelike. The photolithography is used also in the manufacture of thephotomask.

In the manufacture of a photomask by the photolithography, use is madeof a photomask blank having a thin film (e.g. a light-shielding film orthe like) for forming a transfer pattern (mask pattern) on a transparentsubstrate such as a glass substrate. The manufacture of the photomaskusing the photomask blank comprises an exposure process of applyingrequired pattern writing to a resist film formed on the photomask blank,a developing process of developing the resist film according to therequired pattern writing to form a resist pattern, an etching process ofetching the thin film according to the resist pattern, and a process ofstripping and removing the remaining resist pattern. In the developingprocess, a developer is supplied after applying the required patternwriting (exposure) to the resist film formed on the photomask blank todissolve a portion of the resist film soluble in the developer, therebyforming the resist pattern. In the etching process, using this resistpattern as a mask, an exposed portion of the thin film, where the resistpattern is not formed, is dissolved by dry etching or wet etching,thereby forming a required mask pattern on the transparent substrate. Inthis manner, the photomask is produced.

For miniaturization of a pattern of a semiconductor device, it isnecessary to shorten the wavelength of an exposure light source for usein the photolithography in addition to the miniaturization of the maskpattern formed in the photomask. In recent years, the wavelength of anexposure light source in the manufacture of a semiconductor device hasbeen shortened from a KrF excimer laser (wavelength 248 nm) to an ArFexcimer laser (wavelength 193 nm).

As a type of photomask, a halftone phase shift mask is known apart froma conventional binary mask having a light-shielding film pattern made ofa chromium-based material on a transparent substrate. This halftonephase shift mask is configured to have a light-semitransmitting film ona transparent substrate. This light-semitransmitting film is made of,for example, a material containing a molybdenum silicide compound or thelike and is adapted to transmit light having an intensity that does notsubstantially contribute to exposure (e.g. 1% to 20% at an exposurewavelength) and to give a predetermined phase difference to thistransmitted light. By means of light-semitransmitting portions formed bypatterning the light-semitransmitting film and light-transmittingportions formed with no light-semitransmitting film and thus adapted totransmit exposure light, the halftone phase shift mask provides arelationship in which the phase of the light transmitted through thelight-semitransmitting portions is substantially inverted with respectto the phase of the light transmitted through the light-transmittingportions (i.e. shifts the phase). As a consequence, the lights havingpassed near the boundaries between the light-semitransmitting portionsand the light-transmitting portions and bent into the others' regionsdue to the diffraction phenomenon cancel each other out. This makes thelight intensity at the boundaries approximately zero to thereby improvethe contrast, i.e. the resolution, at the boundaries.

In recent years, there have also appeared a binary mask for an ArFexcimer laser using a material containing a molybdenum silicide compoundas a light-shielding film, and the like.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: JP-A-2002-156742-   Patent Document 2: JP-A-2002-258455

SUMMARY OF INVENTION Problem to be Solved by Invention

In the meantime, since the photomask manufacturing cost has beensignificantly increasing following the pattern miniaturization in recentyears, there is an increasing need for a longer lifetime of a photomask.

As a factor for determining the lifetime of a photomask, there is aproblem of mask degradation caused by the repeated use of the photomaskdue to its repeated cleaning. Conventionally, for example, when haze isgenerated, cleaning is carried out for removing the haze, but a filmloss (film dissolution) due to the cleaning cannot be avoided and thus,roughly, the number of times of cleaning determines the mask lifetime.Haze is foreign matter composed mainly of ammonium sulfide and generatedon the mask.

Conventionally, in order to improve the irradiation durability of alight-semitransmitting film, for example, a light-semitransmitting film(phase shift film) composed mainly of a metal and silicon isheat-treated in the atmosphere or an oxygen atmosphere at 250 to 350° C.for 90 to 150 minutes (Patent Document 1) or a cap layer composed mainlyof a metal and silicon is formed on a light-semitransmitting film (phaseshift film) composed mainly of a metal and silicon (Patent Document 2).

The mask lifetime becomes short if the irradiation durability of thelight-semitransmitting film is low, but currently, the irradiationdurability of the light-semitransmitting film is obtained within therange of the mask lifetime based on the number of times of maskcleaning.

Since the number of times of mask cleaning is reduced due to animprovement to haze in recent years, the period of time of the repeateduse of a mask is prolonged and thus the exposure time is prolongedcorrespondingly, and therefore, a problem of the irradiation durabilityparticularly to short-wavelength light such as an ArF excimer laser hasbeen newly actualized.

The present inventors have elucidated that, in the case of a binary maskhaving a metal silicide-based light-shielding film, a phenomenon occursin which the line width changes (increases) due to cumulativeirradiation of an ArF excimer laser (wavelength 193 nm) as an exposurelight source beyond the conventional period of time of the repeated useof the mask. It has been found out that such a line width changedegrades the CD (Critical Dimension) accuracy of the photomask andfinally degrades the CD accuracy of a pattern-transferred wafer, thushindering a further increase in the photomask lifetime.

Further, the present inventors have elucidated that, in the case of aphase shift mask, a phenomenon occurs in which the line width changes(increases) and further the transmittance and the phase differencechange due to the irradiation of an ArF excimer laser (wavelength 193nm) as an exposure light source. In the case of the phase shift mask,such changes in transmittance and phase difference are serious problemsthat affect the mask performance. If the change in transmittance becomeslarge, the transfer accuracy is degraded, while if the change in phasedifference becomes large, the phase shift effect at the patternboundaries is difficult to obtain so that the contrast at the patternboundaries is lowered and thus that the resolution is significantlyreduced.

The problem of the mask degradation due to the repeated use of thephotomask is significant particularly in the case of a phase shift maskin which a compound of a material containing a transition metal andsilicon (transition metal silicide) is used as a material of alight-semitransmitting film. But, also in the case of a binary maskhaving a light-shielding film made of a material containing a transitionmetal and silicon or a compound thereof, there arises a problem ofdegradation in CD accuracy due to a change (increase) in the line widthof the light-shielding film.

Therefore, this invention has been made for solving the conventionalproblems and has an object to provide a photomask blank, a photomask,and methods of manufacturing them, which can improve the irradiationdurability of a thin film composed mainly of a metal and silicon whenexposure light having a wavelength of 200 nm or less is cumulativelyirradiated beyond the conventional period of time of the repeated use ofa mask, thereby improving the photomask lifetime.

Means for Solving the Problem

The present inventors have assumed a cause of the degradation of thephotomask due to its repeated use becoming notable following thereduction in exposure light source wavelength, as follows. As will bedescribed in Examples, it has been elucidated from the results of testsbased on diligent efforts of the present inventors that the effect ofthis invention is exhibited with a predetermined structure of thisinvention, and therefore, this invention is not restricted to anassumption described below.

As a result of examining a pattern of a metal silicide-based thin film(thin film composed mainly of a metal and silicon) in a photomasksubjected to a change (increase) in line width due to its repeated use,the present inventors have elucidated that, as shown in FIG. 3, amodified layer 2′ containing Si, O, and a little metal (e.g. Mo) isformed on the surface layer side of a metal silicide-based thin film 2(e.g. MoSi-based film) and that this is one of main causes of a linewidth change (increase) Δd and changes in transmittance and phasedifference.

The reason (mechanism) for the formation of such a modified layer isconsidered as follows. That is, the conventional sputtered metalsilicide-based thin film (e.g. MoSi-based film) structurally has gapsand, even if annealing is carried out after the film formation, thechange in the structure of the metal silicide-based thin film (e.g. MoSifilm) is small, and therefore, for example, oxygen (O₂), water (H₂O),and the like in the atmosphere and, further, ozone (O₃) and the likeproduced by reaction of oxygen (O₂) in the atmosphere with an ArFexcimer laser enter the gaps and react with Si and Mo forming the metalsilicide-based thin film (e.g. MoSi-based film) in the course of usingthe photomask.

That is, when Si and metal M (e.g. Mo) forming the metal silicide-basedthin film (e.g. MoSi-based film) are subjected to irradiation ofexposure light (particularly short-wavelength light such as an ArFexcimer laser) in such an environment, they are excited into atransition state so that Si is oxidized and expanded (because SiO₂ islarger in volume than Si) and metal M (e.g. Mo) is also oxidized,thereby forming the modified layer on the surface layer side of themetal silicide-based thin film (e.g. MoSi-based film). In this event,the quality of a Si oxide film formed largely differs depending on theamount of water (humidity) in the atmosphere and, as the humidityincreases, the Si oxide film with a lower density is formed. In the casewhere the photomask is repeatedly used in the environment where thelow-density Si oxide film is formed, while being cumulatively subjectedto the irradiation of the exposure light, the oxidation and expansion ofSi further proceed and metal M (e.g. Mo) oxidized at the interfacebetween the bulk and the modified layer diffuses in the modified layerto be deposited on a surface thereof and sublimated as, for example, anoxide of metal M (e.g. MoO₃). Accordingly, the modified layer is furtherreduced in density and thus is in a state where it is easily oxidized.As a result, it is considered that the thickness of the modified layergradually increases (the occupation ratio of the modified layer in themetal silicide-based thin film (e.g. MoSi film) increases).

This phenomenon of the formation and enlargement of the modified layertriggers oxidation reactions of Si and metal M (e.g. Mo) forming themetal silicide-based thin film (e.g. MoSi film) and is significantlyobserved in the case where short-wavelength exposure light such as anArF excimer laser having energy necessary for exciting these constituentatoms into a transition state is irradiated on the metal silicide-basedthin film for an extremely long time. Such a phenomenon is not limitedto the MoSi-based material, but also applies to a light-semitransmittingfilm made of a material containing another transition metal and silicon.Further, this also applies to a binary mask having a light-shieldingfilm made of a material containing a transition metal and silicon.

Based on the elucidated fact and consideration described above, thepresent inventors have paid attention to suppressing the oxidation of athin film such as a metal silicide-based thin film (e.g. MoSi film) as ameasure for suppressing the formation and enlargement of a modifiedlayer and, as a result of further continuing intensive studies, havecompleted this invention.

Specifically, in order to solve the above-mentioned problems, thisinvention has the following structures.

(Structure 1)

A photomask blank for use in the manufacture of a photomask adapted tobe applied with exposure light having a wavelength of 200 nm or less,

wherein the photomask blank has a thin film on a transparent substrate,and

the thin film is made of a material containing a transition metal,silicon, and carbon and comprising silicon carbide and/or a transitionmetal carbide.

(Structure 2)

A photomask blank for use in the manufacture of a photomask adapted tobe applied with exposure light having a wavelength of 200 nm or less,

wherein the photomask blank has a thin film on a transparent substrate,and

the thin film is made of a material containing a transition metal,silicon, and hydrogen and comprising silicon hydride.

(Structure 3)

A photomask blank manufacturing method for use in the manufacture of aphotomask adapted to be applied with exposure light having a wavelengthof 200 nm or less,

the method comprising a step of forming a thin film on a transparentsubstrate,

wherein the thin film is formed by sputtering using a target containingcarbon or an atmospheric gas containing carbon, the thin film containinga transition metal, silicon, and carbon and comprising silicon carbideand/or a transition metal carbide.

(Structure 4)

A photomask blank manufacturing method for use in the manufacture of aphotomask adapted to be applied with exposure light having a wavelengthof 200 nm or less,

the method comprising a step of forming a thin film on a transparentsubstrate,

wherein the thin film is formed by sputtering using an atmospheric gascontaining hydrogen, the thin film containing a transition metal,silicon, and hydrogen and comprising silicon hydride.

(Structure 5)

The photomask blank manufacturing method according to the structure 3,wherein the thin film is formed by adjusting the pressure of theatmospheric gas and/or the power in the sputtering.

(Structure 6)

The photomask blank manufacturing method according to any one ofstructures 1 to 5, wherein the thin film is a light-shielding film.

(Structure 7)

The photomask blank manufacturing method according to any one ofstructures 1 to 5, wherein the thin film is a light-semitransmittingfilm.

(Structure 8)

A method of manufacturing a photomask, comprising a step of patterning,by etching, the thin film in the photomask blank according to any one ofthe structures 1 to 7.

(Structure 9)

A photomask manufactured by using the photomask blank according to anyof the structures 1 to 7.

Effect of the Invention

According to this invention, even if an ArF excimer laser iscontinuously irradiated on a photomask manufactured using a binary maskblank having a metal silicide-based light-shielding film so that thetotal dose becomes 30 kJ/cm² (corresponding to the use of about 100,000times of the photomask and corresponding to the use for about threemonths with a normal frequency of use of the photomask), it is possibleto suppress an increase in the line width (CD change) of alight-shielding film pattern to 10 nm or less and preferably 5 nm orless.

According to this invention, even when an ArF excimer laser iscontinuously irradiated on a photomask manufactured using a phase shiftmask blank having a metal silicide-based light-semitransmitting film sothat the total dose becomes 30 kJ/cm², it is possible to suppress anincrease in the line width (CD change) of a light-semitransmitting filmpattern to 20 nm or less and preferably 10 nm or less. Further, changesin optical properties before and after the ArF excimer laser irradiationare such that the change in transmittance can be within 0.60% and thechange in phase difference can be within 3.0 degrees. Further, thechange in transmittance can be within 0.05% and the change in phasedifference can be within 1.0 degree. In this manner, the changes inoptical properties are suppressed to be small and the changes on thislevel do not affect the performance of the photomask.

According to this invention, it is possible to provide a photomaskblank, a photomask, and methods of manufacturing them, which can improvethe irradiation durability of a thin film such as alight-semitransmitting film to exposure light having a wavelength of 200nm or less, thereby significantly improving the photomask lifetime.

In the half-pitch (hp) 32 nm generation according to the semiconductordevice design rule, it is necessary to set the CD control to 2.6 nm orless on a wafer. For this, the CD change required for a photomask foruse in the hp 32 nm generation is preferably suppressed to 5 nm or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a photomask blank according to an Exampleof this invention.

FIG. 2 is sectional views showing processes of manufacturing a photomaskusing the photomask blank according to the Example of this invention.

FIG. 3 is exemplary diagrams each for explaining an increase in the linewidth of a thin film pattern due to a modified layer formed in a thinfilm of a photomask.

MODE FOR CARRYING OUT THE INVENTION

As in the above-mentioned Structure 1, this invention is a photomaskblank for use in the manufacture of a photomask adapted to be appliedwith exposure light having a wavelength of 200 nm or less,

wherein the photomask blank has a thin film on a transparent substrate,and

the thin film is made of a material containing a transition metal,silicon, and carbon and comprising silicon carbide and/or a transitionmetal carbide.

According to this invention, the oxidation of Si is prevented by thesilicon carbide. It is considered that the oxidation of Si is preventedby the formation of the silicon carbide, which is difficult to oxidize,in the film during sputtering. Further, it is considered that theoxidation of Si is prevented by the formation of stable Si—C bonds inthe film during sputtering.

During the film formation, various bonding states are formed in the thinfilm, but the silicon carbide or Si—C bonds are not always formed.

According to this invention, the oxidation and migration of thetransition metal (M) are suppressed by the transition metal carbide. Itis considered that the oxidation and migration of the transition metal(M) are prevented by the formation of the transition metal carbide,which is difficult to oxidize, in the film during sputtering. Further,it is considered that the oxidation and migration of the transitionmetal (e.g. Mo) are suppressed by the formation of stable M-C bonds inthe film during sputtering.

During the film formation, various bonding states are formed in the thinfilm, but the transition metal carbide or M-C bonds (e.g. Mo—C bonds)are not always formed.

This invention uses the thin film containing carbon in the form of thesilicon carbide and/or the transition metal carbide in the thin filmcontaining the transition metal, silicon, and carbon.

In this invention, since the oxidation of Si is prevented and/or theoxidation and migration of the transition metal (e.g. Mo) aresuppressed, even if the photomask is repeatedly used withshort-wavelength light, such as an ArF excimer laser, having awavelength of 200 nm or less as an exposure light source so that theexposure light with the wavelength of 200 nm or less is cumulativelyirradiated on a thin film pattern of the photomask beyond theconventional period of time of the repeated use, it is possible tosuppress changes in the transfer characteristics of the thin filmpattern such as, for example, a change in the line width thereof andchanges in the transmittance and phase difference of alight-semitransmitting film.

As in the above-mentioned Structure 2, this invention is a photomaskblank for use in the manufacture of a photomask adapted to be appliedwith exposure light having a wavelength of 200 nm or less,

wherein the photomask blank has a thin film on a transparent substrate,and

the thin film is made of a material containing a transition metal,silicon, and hydrogen and comprising silicon hydride.

According to this invention, the oxidation of Si is prevented by thesilicon hydride. It is considered that the oxidation of Si is preventedby the formation of the silicon hydride, which is difficult to oxidize,in the film during sputtering. Further, it is considered that theoxidation of Si is prevented by the formation of anti-oxidation Si—Hbonds during sputtering. Since the hydrogen content does not change evenif an ArF excimer laser is irradiated on the thin film containing thesilicon hydride, it is considered that the Si—H bonds are formed in thesputtering before the ArF excimer laser irradiation.

During the film formation, various bonding states are formed in the thinfilm, but the silicon hydride or Si—H bonds are not always formed.

This invention uses the thin film containing hydrogen in the form of thesilicon hydride in the thin film containing the transition metal,silicon, and hydrogen.

In this invention, since the oxidation of Si is prevented, even if thephotomask is repeatedly used with short-wavelength light, such as an ArFexcimer laser, having a wavelength of 200 nm or less as an exposurelight source so that the exposure light with the wavelength of 200 nm orless is cumulatively irradiated on a thin film pattern of the photomask,it is possible to suppress changes in the transfer characteristics ofthe thin film pattern such as, for example, a change in the line widththereof and changes in the transmittance and phase difference of alight-semitransmitting film.

In this invention, if the thin film containing the transition metal,silicon, and carbon and/or hydrogen satisfies any one of the followingconditions (1) to (3) or a combination thereof [(1)+(2), (1)+(3),(2)+(3), or (1)+(2)+(3)], the irradiation durability is improved so thateven if exposure light having a wavelength of 200 nm or less iscumulatively irradiated beyond the conventional period of time of therepeated use (a modified layer is substantially formed), changes intransfer characteristics due to the modified layer and the like can besuppressed as shown in the following (4) and (5). Further, according tothis invention, the functions and effects shown in the following (6) and(7) can be obtained.

[Conditions]

(1) The thin film is made of a material comprising silicon carbide.

(2) The thin film is made of a material comprising a transition metalcarbide.

(3) The thin film is made of a material comprising silicon hydride.

[Mask CD Change]

(4) The CD change of a light-shielding film pattern can be suppressed to1 to 10 nm or less and preferably 1 to 5 nm or less.

(5) The CD change of a light-semitransmitting film pattern can besuppressed to 1 to 20 nm or less, preferably 1 to 10 nm, and morepreferably 1 to 5 nm or less. With respect to changes in the opticalproperties of the light-semitransmitting film pattern, the change intransmittance can be suppressed to 0.05 to 0.60% or less and the changein phase difference can be suppressed to 1.0 to 3.0 degrees or less.

As shown in FIG. 3, assuming that the thickness of a modified layer 2′formed in a surface layer of a thin film pattern 2 is Δd, the CD changeof the thin film pattern referred to in this invention is defined as2Δd.

FIG. 3, (A) shows the case of a space pattern, wherein CDchange=a−a′=2Δd.

FIG. 3, (B) shows the case of a line pattern, wherein CDchange=a″−a=2Δd.

[Function and Effect]

(6) In this invention, since the etching rate increases due to thepresence of C and/or H (silicon carbide, transition metal carbide,silicon hydride), it is not necessary to increase the thickness of aresist film so that the resolution and the pattern accuracy are notdegraded. Further, since the etching time can be shortened, in the caseof a structure having an etching mask film on a light-shielding film, itis possible to reduce damage to the etching mask film, thus enablingfine patterning.

(7) In this invention, it is possible to suppress precipitation of thetransition metal (e.g. Mo) and thus to prevent deposits on the glasssubstrate or the film due to the precipitation of the transition metal(e.g. Mo). As a consequence, it is possible to suppress defects due tothe deposits.

In this invention, when the thin film comprises two layers or more, Cand/or H (silicon carbide, transition metal carbide, silicon hydride)may be contained in each layer (all the layers) or C and/or H (siliconcarbide, transition metal carbide, silicon hydride) may be containedonly in an arbitrary layer/layers of the plurality of layers.

In this invention, the transition metal (M) comprises any one ofmolybdenum (Mo), tantalum (Ta), chromium (Cr), tungsten (W), titanium(Ti), zirconium (Zr), vanadium (V), niobium (Nb), nickel (Ni), andpalladium (Pd) or an alloy thereof.

The chemical state in the thin film containing the transition metal,silicon, and carbon and/or hydrogen according to this invention containsM (transition metal)-Si bonds, Si—Si bonds, M-M bonds, M-C bonds, Si—Cbonds, and Si—H bonds.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, the content of thetransition metal M is 1 to 50 at % and preferably 4 to 40 at % in thecase of the thin film being a light-shielding film and is 1 to 25 at %and preferably 1 to 15 at % in the case of the thin film being alight-semitransmitting film.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, the silicon content is 30to 95 at % and preferably 50 to 80 at % in the case of the thin filmbeing a light-shielding film and is 20 to 60 at % and preferably 30 to60 at % in the case of the thin film being a light-semitransmittingfilm.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, if the content of thetransition metal is high (in this case, the silicon content becomesrelatively low), deposits on the glass substrate or the film due toprecipitation of the transition metal tend to increase. Accordingly, theratio of the transition metal and silicon is determined taking this intoaccount.

From this point of view, the atomic ratio of the transition metal andsilicon is preferably 1:1 to 1:24 and more preferably 1:4 to 1:15 in thecase of the thin film being a light-shielding film. In the case of thethin film being a light-semitransmitting film, it is preferably 1:1.5 to1:24 and more preferably 1:2 to 1:12.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, the carbon content is 1 to20 at % and preferably 2 to 10 at % in the case of the thin film being alight-shielding film and is 1 to 20 at % and preferably 2 to 10 at %also in the case of the thin film being a light-semitransmitting film.

In the case where the carbon content of the light-shielding film is lessthan 1 at %, the silicon carbide and/or the transition metal carbideare/is difficult to form, while in the case where the carbon contentexceeds 20 at %, it is difficult to reduce the thickness of thelight-shielding film. In the case where the carbon content of thelight-semitransmitting film is less than 1 at %, the silicon carbideand/or the transition metal carbide are/is difficult to form, while inthe case where the carbon content exceeds 20 at %, it is difficult toreduce the thickness of the light-semitransmitting film.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, the hydrogen content is 1to 10 at % and preferably 2 to 5 at % in the case of the thin film beinga light-shielding film and is 1 to 10 at % and preferably 2 to 5 at % inthe case of the thin film being a light-semitransmitting film.

In the case where the hydrogen content of the light-shielding film isless than 1 at %, the silicon hydride is difficult to form, while in thecase where the hydrogen content exceeds 10 at %, it is difficult to formthe film. In the case where the hydrogen content of thelight-semitransmitting film is less than 1 at %, the silicon hydride isdifficult to form, while in the case where the hydrogen content exceeds10 at %, it is difficult to form the film.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, C and/or H (siliconcarbide, transition metal carbide, silicon hydride) may be containedconstantly (uniformly) in its thickness direction.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, the content of C and/or H(silicon carbide, transition metal carbide, silicon hydride) may change(so-called composition gradient) in its thickness direction.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, nitrogen may be containedand the nitrogen content is 0 to 50 at % and preferably 0 to 20 at % inthe case of the thin film being a light-shielding film and is 0 to 60 at% and preferably 0 to 50 at % in the case of the thin film being alight-semitransmitting film.

In the thin film containing the transition metal, silicon, and carbonand/or hydrogen according to this invention, oxygen may be contained.However, oxygen easily bonds to form Si—O and Mo—O before Si—C, Mo—C, orSi—H is formed and, therefore, it is better not to add much. The thinfilm may also be substantially free of oxygen.

When the thin film is a light-shielding film, the oxygen content ispreferably 0 to 60 at %. When the light-shielding film is in the form ofa plurality of layers comprising an antireflection layer and alight-shielding layer, the oxygen content is 0 to 60 at % in theantireflection layer and is 0 to 20 at % and preferably 0 to 10 at % inthe light-shielding layer. When the thin film is alight-semitransmitting film, the oxygen content is preferably 0 to 60 at%.

In this invention, in order to reduce the thickness of a resist film tothereby form a fine pattern, the structure may have an etching mask filmon the light-shielding film. This etching mask film is made of amaterial comprising chromium having etching selectivity (having etchingresistance) to etching of the light-shielding film containing thetransition metal silicide or comprising a chromium compound in which anelement/elements such as oxygen, nitrogen, and carbon is/are added tochromium.

In this invention, the thickness of the resist film is preferably 75 nmor less and the thickness of the etching mask film is preferably 5 nm ormore and 15 nm or less. This is because, in relation to shortening theetching time of the etching mask film, the thickness of the Cr-basedetching mask film is preferably 5 nm or more and 15 nm or less when thethickness of the resist film is 75 nm or less, in terms of reducing LER(Line Edge Roughness) of a resist pattern.

Likewise, in this invention, the thickness of the resist film ispreferably 65 nm or less and the thickness of the etching mask film ispreferably 5 nm or more and 10 nm or less.

In this invention, the photomask blank may be a binary mask blank or aphase shift mask blank.

A phase shift mask may be a phase shift mask of the halftone type(tri-tone type), the Levenson type, the auxiliary pattern type, theself-aligned type (edge-enhanced type), or the like.

In one aspect of this invention, the thin film is a light-shielding film(Structure 6 described above).

The light-shielding film may have a single-layer structure or aplural-layer structure.

The light-shielding film may be configured to comprise an antireflectionlayer.

The light-shielding film may be a composition gradient film.

The light-shielding film may have a three-layer structure comprising aback-surface antireflection layer, a light-shielding layer, and afront-surface antireflection layer.

The light-shielding film may have a two-layer structure comprising alight-shielding layer and a front-surface antireflection layer.

In the case where the light-shielding film has the plural-layerstructure, C and/or H (silicon carbide, transition metal carbide,silicon hydride) may be contained in all the layers or C and/or H(silicon carbide, transition metal carbide, silicon hydride) may becontained only in the arbitrary layer such as, for example, thelight-shielding layer.

In this invention, the light-shielding film is preferably a transitionmetal silicide carbide hydride, a transition metal silicide carbide, atransition metal silicide hydride, a transition metal silicide nitridecarbide hydride, a transition metal silicide nitride carbide, or atransition metal silicide nitride hydride.

In this invention, the following aspect is included.

A photomask blank for use in the manufacture of a photomask adapted tobe applied with exposure light having a wavelength of 200 nm or less,

wherein the photomask blank has a light-shielding film on a transparentsubstrate,

the light-shielding film comprises at least three layers, and

the light-shielding film comprises

a light-shielding layer made of a material containing a transitionmetal, silicon, and carbon and/or hydrogen and comprising at least onekind of silicon carbide, a transition metal carbide, and siliconhydride,

an antireflection layer formed in contact with and above thelight-shielding layer and made of a transition metal silicide compoundcontaining at least one of oxygen and nitrogen, and

a low reflection layer formed in contact with and below thelight-shielding layer and made of a transition metal silicide compoundcontaining at least one of oxygen and nitrogen.

In this invention, when the light-shielding film is formed of molybdenumsilicide compounds and has a two-layer structure of a light-shieldinglayer (MoSi or the like) and a front-surface antireflection layer(MoSiON or the like) or a three-layer structure further comprising aback-surface antireflection layer (MoSiON, MoSiN, or the like) betweenthe light-shielding layer and the substrate, the content ratio of Mo andSi in the molybdenum silicide compound of the light-shielding layer ispreferably one of the following A, B, and C.

(A) In terms of the light-shielding properties, Mo is preferably 4% ormore and 40% or less (preferably 9% or more and 40% or less, morepreferably 15% or more and 40% or less, and further preferably 20% ormore and 40% or less).

(B) In terms of the cleaning resistance, the Mo content of theantireflection layer is 0 to 20 at %, preferably 0 to 10 at %, and morepreferably 0 to 5 at %.

(C) In terms of the pattern sectional shape control, the etching rate ofthe antireflection layer and the etching rate of the light-shieldinglayer should be matched with each other and it is preferable that Mo inthe molybdenum silicide light-shielding layer be set to 4% or more and40% or less and preferably 10% or more and 40% or less with respect tothe oxidized and/or nitrided antireflection layer.

According to the above-mentioned structure of this invention, i.e. thelight-shielding layer containing molybdenum silicide in which themolybdenum content is 4 at % or more and 40 at % or less, the followingfunctions and effects are obtained.

The following functions and effects are obtained by a reduction inthickness of the light-shielding film (reduction in thickness of a maskpattern).

(a) It is possible to achieve prevention of mask pattern collapse inmask cleaning.

(b) With the reduction in thickness of the light-shielding film, theside wall height of the mask pattern is also reduced and, therefore, thepattern accuracy particularly in the side wall height direction isimproved so that the CD accuracy (particularly the linearity) can beenhanced.

(c) With respect to a photomask particularly for use in the hyper-NA(Numerical Aperture) (immersion) generation, it is necessary to reducethe thickness of a mask pattern (reduce the side wall height of the maskpattern) as a shadowing measure and this requirement can be satisfied.

When the Mo content of the light-shielding layer is within the scope ofthis invention, the following functions and effects are obtained.

(d) As compared with the composition which falls outside the scope ofthis invention, the perpendicular etching sectional shape is obtained.

The light-shielding film may be a composition gradient film in which thecomposition in its thickness direction changes continuously or stepwise.

In this invention, in the case where the light-shielding film has aplural-layer structure such as a three-layer structure comprising aback-surface antireflection layer, a light-shielding layer, and afront-surface antireflection layer or a two-layer structure comprising alight-shielding layer and a front-surface antireflection layer, thelight-shielding layer made of a molybdenum silicide metal preferably hasa thickness of 20 nm to 50 nm or less and more preferably 25 nm to 40nm. The front-surface antireflection layer and the back-surfaceantireflection layer each preferably have a thickness of 5 nm to 20 nmand more preferably 7 nm to 15 nm.

In this invention, an etching mask film may be provided on thelight-shielding film.

By providing the etching mask film, the thickness of a resist film canbe reduced so that a finer pattern can be formed.

In the case where the light-shielding film is made of a transition metalsilicide (MSi-based), the etching mask film may be made of a material(Cr-based material) comprising chromium having etching selectivity(having etching resistance) to etching of the light-shielding film orcomprising a chromium compound in which an element/elements such asoxygen, nitrogen, and carbon is/are added to chromium.

In the case where the light-shielding film is made of a Cr-basedmaterial, the etching mask film may be made of a MSi-based material. Inthis case, if an antireflection function is given to the etching maskfilm so that the etching mask film remains, C and/or H (silicon carbide,transition metal carbide, silicon hydride) may be contained in theetching mask film. This invention includes an aspect in which the thinfilm containing the transition metal, silicon, and carbon and/orhydrogen is an etching mask film.

The Cr-based material has high etching selectivity for a fluorine-basedgas with respect to the MoSi-based material. However, since the Cr-basedmaterial is not a little subjected to the physical etching influenceduring etching with the fluorine-based gas and thus is more or lessreduced in amount. Accordingly, even if the Cr-based etching mask filmis optimized, the thickness of the MoSi-based light-shielding film hasan upper limit. When the thickness of the MoSi-based light-shieldingfilm exceeds 60 nm with respect to the effective Cr-based etching maskfilm thickness, the etching time of dry etching with the fluorine-basedgas is prolonged so that the thickness of the Cr-based etching mask filmafter this dry etching is reduced and thus LER (Line Edge Roughness) ofa Cr-based etching mask film pattern is degraded. Therefore, thethickness of the MoSi-based light-shielding film (the total thickness inthe case of the two-layer or three-layer structure) is preferably 60 nmor less.

In another aspect of this invention, the thin film is alight-semitransmitting film (Structure 7 described above).

The light-semitransmitting film may have a single-layer structure, atwo-layer structure comprising a low-transmittance layer and ahigh-transmittance layer, or a multilayer structure.

The light-semitransmitting film may be of the high-transmittance type.The high-transmittance type has, for example, a relatively hightransmittance of 10 to 40% while the transmittance is normally 1% toless than 10%.

In this invention, the thickness of the light-semitransmitting film ispreferably 50 to 150 nm.

This invention includes a photomask and a photomask blank having alight-shielding film (pattern) in addition to a light-semitransmittingfilm (pattern). In this case, it may be configured that thelight-shielding film (pattern) is formed on the upper layer side of thelight-semitransmitting film (pattern) or on the lower layer side of thelight-semitransmitting film (pattern).

In the case where the light-semitransmitting film is made of atransition metal silicide (MSi-based), the light-shielding film may bemade of a material (Cr-based material) comprising chromium havingetching selectivity (having etching resistance) to etching of thelight-semitransmitting film or comprising a chromium compound in whichan element/elements such as oxygen, nitrogen, and carbon is/are added tochromium.

In the case where the light-semitransmitting film and thelight-shielding film are made of the same transition metal silicide(MSi-based), an etching stopper film made of a Cr-based material may beprovided between the light-semitransmitting film and the light-shieldingfilm.

In this invention, the light-semitransmitting film is preferably atransition metal silicide nitride carbide hydride, a transition metalsilicide nitride carbide, or a transition metal silicide nitridehydride.

As in the above-mentioned Structure 3, a photomask blank manufacturingmethod of this invention is a method of manufacturing a photomask blankfor use in the manufacture of a photomask adapted to be applied withexposure light having a wavelength of 200 nm or less,

the method comprising a step of forming a thin film on a transparentsubstrate,

wherein the thin film is formed by sputtering using a target containingcarbon or an atmospheric gas containing carbon, the thin film containinga transition metal, silicon, and carbon and comprising silicon carbideand/or a transition metal carbide.

Herein, a hydrocarbon gas is, for example, methane (CH₄), ethane (C₂H₆),propane (C₃H₈), butane (C₄H₁₀), or the like.

Using the hydrocarbon gas, carbon and hydrogen (silicon carbide,transition metal carbide, silicon hydride) can be introduced into thefilm.

Using the target containing carbon, only the carbon (silicon carbide,transition metal carbide) can be introduced into the film. In this case,there are included, in addition to an aspect of using a MoSiC target, anaspect of using a Mo target and a Si target one or both of which containC and an aspect of using a MoSi target and a C target.

As in the above-mentioned Structure 4, a photomask blank manufacturingmethod of this invention is a method of manufacturing a photomask blankfor use in the manufacture of a photomask adapted to be applied withexposure light having a wavelength of 200 nm or less,

the method comprising a step of forming a thin film on a transparentsubstrate,

wherein the thin film is formed by sputtering using an atmospheric gascontaining hydrogen, the thin film containing a transition metal,silicon, and hydrogen and comprising silicon hydride.

This makes it possible to introduce only hydrogen (silicon hydride) intothe film.

This method includes, in addition to an aspect of using a MoSi target,an aspect of using a Mo target and a Si target. When carbon (siliconcarbide, transition metal carbide) is caused to be further contained inthe film by this method, there are included, in addition to an aspect ofusing a MoSiC target, an aspect of using a Mo target and a Si target oneor both of which contain C and an aspect of using a MoSi target and a Ctarget.

In this invention, as in the above-mentioned Structure 5, the thin filmis preferably formed by adjusting the pressure of the atmospheric gasand/or the power in the sputtering.

It is considered that when the pressure of the atmospheric gas is low(in this case, the film formation rate is low), carbides or the like(silicon carbide, transition metal carbide) tend to be formed. Further,it is considered that when the electric power (power) is low, carbidesor the like (silicon carbide, transition metal carbide) tend to beformed.

This invention adjusts the pressure of the atmospheric gas and/or thepower in the sputtering, thereby forming the carbides or the like(silicon carbide, transition metal carbide) as described above to obtainthe above-mentioned functions and effects of this invention.

This invention adjusts the pressure of the atmospheric gas and/or thepower in the sputtering, thereby forming stable Si—C bonds and/or stabletransition metal M-C bonds in the film during the sputtering to obtainthe above-mentioned functions and effects of this invention.

On the other hand, it is considered that when the pressure of theatmospheric gas is high (in this case, the film formation rate is high),carbides or the like (silicon carbide, transition metal carbide) aredifficult to form. Further, it is considered that when the electricpower (power) is high, carbides or the like (silicon carbide, transitionmetal carbide) are difficult to form.

In this invention, a heat treatment may be carried out after forming thethin film or after manufacturing the photomask. This is because Si—Obonds are formed in a thin film surface or in pattern side walls so thatthe chemical resistance is improved.

The heat treatment in an atmosphere containing oxygen at 200° C. to 900°C. is preferably cited. If the heating temperature is less than 200° C.,there is a problem that the cleaning resistance and the hot waterresistance are reduced. On the other hand, if the heating temperature ishigher than 900° C., there arises a possibility of degradation of thethin film itself.

In this invention, ultraviolet irradiation, preferably ArF excimer laserirradiation, may be carried out in advance after forming the film orafter manufacturing the mask. This is because silicon carbide and/or atransition metal carbide are further formed so that the irradiationdurability is further improved.

The transparent substrate is not particularly limited as long as it hastransparency at an exposure wavelength to be used. In this invention, asynthetic quartz substrate, a quartz substrate, and various other glasssubstrates (e.g. CaF₂ substrate, soda-lime glass, aluminosilicate glass,alkali-free glass substrate, low thermal expansion glass substrate,etc.) can be used and, among them, the quartz substrate is particularlysuitable for this invention because it has high transparency in therange of ArF excimer laser to shorter wavelengths.

As a method of forming the thin film on the transparent substrate, asputtering film forming method, for example, is preferably cited, butthis invention is not limited to the sputtering film forming method.

A DC magnetron sputtering apparatus is preferably cited as a sputteringapparatus, but this invention is not limited to this film formingapparatus. Another type of sputtering apparatus such as an RF magnetronsputtering apparatus may alternatively be used.

As in the above-mentioned Structure 8, this invention provides aphotomask manufacturing method comprising a step of patterning, byetching, the thin film in the above-mentioned photomask blank obtainedby this invention.

As the etching in this event, dry etching which is effective for forminga fine pattern is suitably used.

According to such a photomask manufacturing method, there is obtained aphotomask which is improved in the irradiation durability of a thin filmcomposed mainly of a metal and silicon when exposure light, such as anArF excimer laser, having a wavelength of 200 nm or less is cumulativelyirradiated beyond the conventional period of time of the repeated use ofthe mask, and which as a result is significantly improved in thelifetime of the photomask.

As in the above-mentioned Structure 9, a photomask of this invention ismanufactured by using the above-mentioned photomask blank according tothis invention.

As a consequence, there is obtained a photomask which is improved in theirradiation durability of a thin film composed mainly of a metal andsilicon when exposure light, such as an ArF excimer laser, having awavelength of 200 nm or less is cumulatively irradiated beyond theconventional period of time of the repeated use of the mask, and whichas a result is significantly improved in the lifetime of the photomask.

In this invention, for dry-etching the molybdenum silicide-based thinfilm, use can be made of, for example, a fluorine-based gas such as SF₆,CF₄, C₂F₆, or CHF₃, a mixed gas of such a fluorine-based gas and He, H₂,N₂, Ar, C₂H₄, O₂ or the like, a chlorine-based gas such as Cl₂ orCH₂Cl₂, or a mixed gas of such a chlorine-based gas and He, H₂, N₂, Ar,C₂H₄, or the like.

In this invention, for dry-etching the chromium-based thin film, it ispreferable to use a dry etching gas in the form of a chlorine-based gasor in the form of a mixed gas containing a chlorine-based gas and anoxygen gas. This is because if the chromium-based thin film made of thematerial containing chromium and the element/elements such as oxygen andnitrogen is dry-etched using the above-mentioned dry etching gas, it ispossible to increase the dry etching rate and thus to shorten the dryetching time so that a light-shielding film pattern with an excellentsectional shape can be formed. As the chlorine-based gas for use as thedry etching gas, there can be cited, for example, Cl₂, SiCl₄, HCl, CCl₄,CHCl₃, or the like.

EXAMPLES

Hereinbelow, the embodiments of this invention will be described infurther detail with reference to Examples.

Example 1

FIG. 1 is a sectional view of a binary mask blank 10 of Example 1.

Using a synthetic quartz glass substrate having a 6-inch square sizewith a thickness of 0.25 inches as a transparent substrate 1, a MoSiONfilm (back-surface antireflection layer), a MoSiCH film (light-shieldinglayer), and a MoSiON film (front-surface antireflection layer) wereformed as a thin film 2 (light-shielding film) on the transparentsubstrate 1.

Specifically, using a mixed target of Mo and Si (Mo:Si=21 mol %:79 mol%), a film made of molybdenum, silicon, oxygen, and nitrogen (Mo: 13.0at %, Si: 36.3 at %, O: 3.1 at %, N: 47.7 at %) and having a thicknessof 7 nm was formed by setting the power of a DC power supply to 3.0 kWin a mixed gas atmosphere of Ar, O₂, N₂, and He (gas flow rate ratioAr:O₂:N₂:He=5:4:49:42) at a gas pressure of 0.2 Pa, thereby forming theMoSiON film (back-surface antireflection layer).

Then, using a target of Mo:Si=21 mol %:79 mol %, a film made ofmolybdenum, silicon, carbon, and hydrogen (Mo: 19.8 at %, Si: 76.7 at %,C: 2.0 at %, H: 1.5 at %) and having a thickness of 30 nm was formed bysetting the power of a DC power supply to 2.0 kW in a mixed gasatmosphere of Ar, CH₄, and He (gas flow rate ratio Ar:CH₄:He=10:1:50) ata gas pressure of 0.3 Pa, thereby forming the MoSiCH film(light-shielding layer).

Then, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 15 nm was formedby setting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, andHe (gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1Pa, thereby forming the MoSiON film (front-surface antireflectionlayer).

The total thickness of the light-shielding film was set to 52 nm. Theoptical density (OD: Optical Density) of the light-shielding film was3.0 at the wavelength 193 nm of ArF excimer laser exposure light.

In the manner described above, a binary mask blank of Example 1 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank. FIG.2 is sectional views showing processes of manufacturing the binary maskusing the binary mask blank.

First, a chemically amplified positive resist film for electron beamwriting (PRL009 manufactured by FUJIFILM Electronic Materials Co., Ltd.)was formed as a resist film 3 on the mask blank 10 (see FIG. 2, (A)).

Then, using an electron beam writing apparatus, a required pattern waswritten on the resist film 3 formed on the mask blank 10 and,thereafter, the resist film 3 was developed with a predetermineddeveloper, thereby forming a resist pattern 3 a (see FIG. 2, (B) and(C)).

Then, using the resist pattern 3 a as a mask, the thin film 2 in theform of the three-layer structure light-shielding film was etched,thereby forming a light-shielding film pattern 2 a (see FIG. 2, (D)). Amixed gas of SF₆ and He was used as a dry etching gas.

Then, the remaining resist pattern was stripped, thereby obtaining abinary mask 20 of Example 1 (see FIG. 2, (E)). There was almost nochange in the optical density (OD) of the light-shielding film at thewavelength 193 nm of ArF excimer laser exposure light as compared withthat at the time of the manufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask 20 so that the total dose became 30 kJ/cm². Herein, the dose of 30kJ/cm² (energy density: about 25 mJ/cm²) corresponds to the use of about100,000 times of a photomask and corresponds to the use for about threemonths with a normal frequency of use of a photomask.

A section of the light-shielding film pattern after the ArF excimerlaser irradiation was observed in detail using a TEM (transmissionelectron microscope). As a result, a modified layer as conventionallyformed was not particularly confirmed and, further, an increase in linewidth (CD change) was suppressed to 2 nm or less. Therefore, it is seenthat the binary mask blank and the binary mask of Example 1 haveextremely high irradiation durability to cumulative irradiation of anexposure light source with a short wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture at 23° C. for 60 minutes and in hot water at 90° C. for60 minutes, thereby examining the chemical resistance thereof,particularly the chemical resistance (ammonia hydrogen peroxide mixtureresistance, hot water resistance) of pattern side walls. As a result,corrosion of the pattern side walls was not confirmed in either case andthus the chemical resistance was excellent.

Further, as a result of observing in detail a mask surface after the ArFexcimer laser irradiation, deposits due to precipitation of Mo asconventionally formed were not particularly confirmed on the transparentsubstrate (glass substrate) or the film.

Example 2

A three-layer structure light-shielding film (MoSiON film (back-surfaceantireflection layer)/MoSiCH film (light-shielding layer)/MoSiON film(front-surface antireflection layer)) was formed on a transparentsubstrate in completely the same manner as in Example 1. The totalthickness of the light-shielding film and the optical density (OD) ofthe light-shielding film were approximately the same as those in Example1 at the wavelength 193 nm of ArF excimer laser exposure light.

Thereafter, a heat treatment was applied to the transparent substrateformed with the light-shielding film. Specifically, using a heatingfurnace, the heat treatment was carried out in the atmosphere at aheating temperature of 450° C. The contents of C and H in the MoSiCHfilm (light-shielding layer) of the light-shielding film did not changeafter the heat treatment.

In the manner described above, a binary mask blank of Example 2 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1.

An ArF excimer laser was continuously irradiated on the obtained binarymask so that the total dose became 30 kJ/cm². A section of alight-shielding film pattern after the ArF excimer laser irradiation wasobserved in detail using a TEM (transmission electron microscope). As aresult, a modified layer as conventionally formed was not particularlyconfirmed and, further, an increase in line width (CD change) wassuppressed to 2 nm or less. Therefore, it is seen that the binary maskblank and the binary mask of Example 2 have extremely high irradiationdurability to cumulative irradiation of an exposure light source with ashort wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after the ArFexcimer laser irradiation, deposits due to precipitation of Mo asconventionally formed were not particularly confirmed on the transparentsubstrate (glass substrate) or the film.

Example 3

Example 3 is the same as Example 1 except that a MoSiON film(back-surface antireflection layer) and a MoSiCH film (light-shieldinglayer) in a light-shielding film were formed under the followingconditions so that the thickness and the Si content of each of theMoSiON film (back-surface antireflection layer) and the MoSiCH film(light-shielding layer) were changed and that the total thickness of thelight-shielding film was changed.

Specifically, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 7 nm was formed bysetting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, and He(gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1 Pa,thereby forming the MoSiON film (back-surface antireflection layer).

Then, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, carbon, and hydrogen (Mo: 3.9 at %, Si: 92.6 at %,C: 2.0 at %, H: 1.5 at %) and having a thickness of 38 nm was formed bysetting the power of a DC power supply to 2.0 kW in a mixed gasatmosphere of Ar, CH₄, and He (gas flow rate ratio Ar:CH₄:He=10:1:50) ata gas pressure of 0.3 Pa, thereby forming the MoSiCH film(light-shielding layer).

Then, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 15 nm was formedby setting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, andHe (gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1Pa, thereby forming the MoSiON film (front-surface antireflectionlayer).

The total thickness of the light-shielding film was set to 60 nm. Theoptical density (OD) of the light-shielding film was 3.0 at thewavelength 193 nm of ArF excimer laser exposure light.

In the manner described above, a binary mask blank of Example 3 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1. There was almost no change in the opticaldensity (OD) of the light-shielding film at the wavelength 193 nm of ArFexcimer laser exposure light as compared with that at the time of themanufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask so that the total dose became 30 kJ/cm². A section of alight-shielding film pattern after the ArF excimer laser irradiation wasobserved in detail using a TEM (transmission electron microscope). As aresult, a modified layer as conventionally formed was not particularlyconfirmed and, further, an increase in line width (CD change) wassuppressed to 5 nm or less. Therefore, it is seen that the binary maskblank and the binary mask of Example 3 have extremely high irradiationdurability to cumulative irradiation of an exposure light source with ashort wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after theirradiation, deposits due to precipitation of Mo as conventionallyformed were not particularly confirmed on the transparent substrate(glass substrate) or the film.

Example 4

Example 4 is the same as Example 2 except that a MoSiCH film(light-shielding layer) in a light-shielding film was formed under thefollowing conditions so that the flow rate ratio of a CH₄ gas in thefilm formation and the contents of C and H in the MoSiCH film(light-shielding layer) were changed.

Specifically, using a mixed target of Mo and Si (Mo:Si=21 mol %:79 mol%), a film made of molybdenum, silicon, oxygen, and nitrogen (Mo: 13.0at %, Si: 36.3 at %, O: 3.1 at %, N: 47.7 at %) and having a thicknessof 7 nm was formed by setting the power of a DC power supply to 3.0 kWin a mixed gas atmosphere of Ar, O₂, N₂, and He (gas flow rate ratioAr:O₂:N₂:He=5:4:49:42) at a gas pressure of 0.2 Pa, thereby forming theMoSiON film (back-surface antireflection layer).

Then, using a target of Mo:Si=21 mol %:79 mol %, a film made ofmolybdenum, silicon, carbon, and hydrogen (Mo: 20.6 at %, Si: 77.4 at %,C: 1.0 at %, H: 1.0 at %) and having a thickness of 30 nm was formed bysetting the power of a DC power supply to 2.0 kW in a mixed gasatmosphere of Ar, CH₄, and He (gas flow rate ratio Ar:CH₄:He=10:1:65) ata gas pressure of 0.3 Pa, thereby forming the MoSiCH film(light-shielding layer).

Then, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 15 nm was formedby setting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, andHe (gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1Pa, thereby forming the MoSiON film (front-surface antireflectionlayer).

The total thickness of the light-shielding film was set to 52 nm. Theoptical density (OD) of the light-shielding film was 3.0 at thewavelength 193 nm of ArF excimer laser exposure light.

Thereafter, a heat treatment was applied to the transparent substrateformed with the light-shielding film. Specifically, using a heatingfurnace, the heat treatment was carried out in the atmosphere at aheating temperature of 450° C. The contents of C and H in the MoSiCHfilm (light-shielding layer) of the light-shielding film did not changeafter the heat treatment.

In the manner described above, a binary mask blank of Example 4 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1. There was almost no change in the opticaldensity (OD) of the light-shielding film at the wavelength 193 nm of ArFexcimer laser exposure light as compared with that at the time of themanufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask so that the total dose became 30 kJ/cm². A section of alight-shielding film pattern after the ArF excimer laser irradiation wasobserved in detail using a TEM (transmission electron microscope). As aresult, a modified layer as conventionally formed was not particularlyconfirmed and, further, an increase in line width (CD change) wassuppressed to 5 nm or less. Therefore, it is seen that the binary maskblank and the binary mask of Example 4 have extremely high irradiationdurability to cumulative irradiation of an exposure light source with ashort wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after the ArFexcimer laser irradiation, deposits due to precipitation of Mo asconventionally formed were not particularly confirmed on the transparentsubstrate (glass substrate) or the film.

Example 5

Example 5 is the same as Example 1 except that a MoSiON film(back-surface antireflection layer) in a light-shielding film was formedunder the following conditions so that the MoSiON film (back-surfaceantireflection layer) was changed to a MoSiN film (back-surfaceantireflection layer), that the thickness and the Si content thereofwere changed, and that the total thickness of the light-shielding filmwas changed.

Specifically, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, and nitrogen (Mo: 2.3 at %, Si: 56.5 at %, N: 41.1at %) and having a thickness of 13 nm was formed by setting the power ofa DC power supply to 3.0 kW in Ar, N₂, and He (gas flow rate ratioAr:N₂:He=6:11:16) at a gas pressure of 0.1 Pa, thereby forming the MoSiNfilm (back-surface antireflection layer).

Then, using a target of Mo:Si=21 mol %:79 mol %, a film made ofmolybdenum, silicon, carbon, and hydrogen (Mo: 19.8 at %, Si: 76.7 at %,C: 2.0 at %, H: 1.5 at %) and having a thickness of 30 nm was formed bysetting the power of a DC power supply to 2.0 kW in a mixed gasatmosphere of Ar, CH₄, and He (gas flow rate ratio Ar:CH₄:He=10:1:50) ata gas pressure of 0.3 Pa, thereby forming the MoSiCH film(light-shielding layer).

Then, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 15 nm was formedby setting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, andHe (gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1Pa, thereby forming the MoSiON film (front-surface antireflectionlayer).

The total thickness of the light-shielding film was set to 58 nm. Theoptical density (OD) of the light-shielding film was 3.0 at thewavelength 193 nm of ArF excimer laser exposure light.

In the manner described above, a binary mask blank of Example 5 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1. There was almost no change in the opticaldensity (OD) of the light-shielding film at the wavelength 193 nm of ArFexcimer laser exposure light as compared with that at the time of themanufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask so that the total dose became 30 kJ/cm². A section of alight-shielding film pattern after the ArF excimer laser irradiation wasobserved in detail using a TEM (transmission electron microscope). As aresult, a modified layer as conventionally formed was not particularlyconfirmed and, further, an increase in line width (CD change) wassuppressed to 2 nm or less. Therefore, it is seen that the binary maskblank and the binary mask of Example 5 have extremely high irradiationdurability to cumulative irradiation of an exposure light source with ashort wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after the ArFexcimer laser irradiation, deposits due to precipitation of Mo asconventionally formed were not particularly confirmed on the transparentsubstrate (glass substrate) or the film.

Example 6

Example 6 is the same as Example 1 except that a MoSiON film(back-surface antireflection layer) in a light-shielding film was formedunder the following conditions so that the thickness and the Si contentthereof were changed and that the total thickness of the light-shieldingfilm was changed.

Specifically, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 15 nm was formedby setting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, andHe (gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1Pa, thereby forming the MoSiON film (back-surface antireflection layer).

Then, using a target of Mo:Si=21 mol %:79 mol %, a film made ofmolybdenum, silicon, carbon, and hydrogen (Mo: 19.8 at %, Si: 76.7 at %,C: 2.0 at %, H: 1.5 at %) and having a thickness of 30 nm was formed bysetting the power of a DC power supply to 2.0 kW in a mixed gasatmosphere of Ar, CH₄, and He (gas flow rate ratio Ar:CH₄:He=10:1:50) ata gas pressure of 0.3 Pa, thereby forming the MoSiCH film(light-shielding layer).

Then, using a target of Mo:Si=4 mol %:96 mol %, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) and having a thickness of 15 nm was formedby setting the power of a DC power supply to 3.0 kW in Ar, O₂, N₂, andHe (gas flow rate ratio Ar:O₂:N₂:He=6:5:11:16) at a gas pressure of 0.1Pa, thereby forming the MoSiON film (front-surface antireflectionlayer).

The total thickness of the light-shielding film was set to 60 nm. Theoptical density (OD) of the light-shielding film was 3.0 at thewavelength 193 nm of ArF excimer laser exposure light.

In the manner described above, a binary mask blank of Example 6 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1. There was almost no change in the opticaldensity (OD) of the light-shielding film at the wavelength 193 nm of ArFexcimer laser exposure light as compared with that at the time of themanufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask so that the total dose became 30 kJ/cm². A section of alight-shielding film pattern after the ArF excimer laser irradiation wasobserved in detail using a TEM (transmission electron microscope). As aresult, a modified layer as conventionally formed was not particularlyconfirmed and, further, an increase in line width (CD change) wassuppressed to 2 nm or less. Therefore, it is seen that the binary maskblank and the binary mask of Example 6 have extremely high irradiationdurability to cumulative irradiation of an exposure light source with ashort wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after theirradiation, deposits due to precipitation of Mo as conventionallyformed were not particularly confirmed on the glass substrate or thefilm.

Example 7

Example 7 is the same as Example 1 except the following points.

With respect to a light-shielding film, a MoSiON film (back-surfaceantireflection layer) was not formed.

A MoSiCH film (light-shielding layer) and a MoSiON film (front-surfaceantireflection layer) in the light-shielding film were formed under thefollowing conditions so that the MoSiCH film (light-shielding layer) waschanged to a MoSiCHN film (light-shielding layer), that the thicknessand the Si content thereof were changed, and that the thickness of theMoSiON film (front-surface antireflection layer) was changed.

The total thickness of the light-shielding film was changed.

As the MoSiCHN film (light-shielding layer) in the light-shielding film,a film made of molybdenum, silicon, carbon, hydrogen, and nitrogen (Mo:7.1 at %, Si: 71.7 at %, C: 2.0 at %, H: 1.0 at %, N: 18.2 at %) wasformed to a thickness of 52 nm. As the MoSiON film (front-surfaceantireflection layer) in the light-shielding film, a film made ofmolybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si: 57.1 at %,O: 15.9 at %, N: 24.1 at %) was formed to a thickness of 8 nm.

The total thickness of the light-shielding film was set to 60 nm. Theoptical density (OD) of the light-shielding film was 3.0 at thewavelength 193 nm of ArF excimer laser exposure light.

In the manner described above, a binary mask blank of Example 7 wasmanufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1. There was almost no change in the opticaldensity (OD) of the light-shielding film at the wavelength 193 nm of ArFexcimer laser exposure light as compared with that at the time of themanufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask so that the total dose became 30 kJ/cm². A section of alight-shielding film pattern after the ArF excimer laser irradiation wasobserved in detail using a TEM (transmission electron microscope). As aresult, a modified layer as conventionally formed was not particularlyconfirmed and, further, an increase in line width (CD change) wassuppressed to 10 nm or less. Therefore, it is seen that the binary maskblank and the binary mask of Example 7 have extremely high irradiationdurability to cumulative irradiation of an exposure light source with ashort wavelength of 200 nm or less.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after theirradiation, deposits due to precipitation of Mo as conventionallyformed were not particularly confirmed on the transparent substrate(glass substrate) or the film.

Comparative Example 1

Comparative Example 1 is the same as Example 1 except the followingpoints.

With respect to a light-shielding film, a MoSiON film (back-surfaceantireflection layer) was not formed.

A MoSi film (light-shielding layer) and a MoSiON film (front-surfaceantireflection layer) in the light-shielding film were formed under thefollowing conditions so that the MoSi film (light-shielding layer) waschanged to a MoSiN film (light-shielding layer), that the thickness andthe Si content thereof were changed, and that the thickness of theMoSiON film (front-surface antireflection layer) was changed.

The total thickness of the light-shielding film was changed.

As the MoSiN film (light-shielding layer) in the light-shielding film, afilm made of molybdenum, silicon, and nitrogen (Mo: 9 at %, Si: 72.8 at%, N: 18.2 at %) was formed to a thickness of 52 nm. As the MoSiON film(front-surface antireflection layer) in the light-shielding film, a filmmade of molybdenum, silicon, oxygen, and nitrogen (Mo: 2.6 at %, Si:57.1 at %, O: 15.9 at %, N: 24.1 at %) was formed to a thickness of 8nm.

The total thickness of the light-shielding film was set to 60 nm. Theoptical density (OD) of the light-shielding film was 3.0 at thewavelength 193 nm of ArF excimer laser exposure light.

In the manner described above, a binary mask blank of ComparativeExample 1 was manufactured.

Then, a binary mask was manufactured using this binary mask blank in thesame manner as in Example 1. There was almost no change in the opticaldensity (OD) of the light-shielding film at the wavelength 193 nm of ArFexcimer laser exposure light as compared with that at the time of themanufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained binarymask of Comparative Example 1 so that the total dose became 30 kJ/cm².The optical density (OD) of the light-shielding film after theirradiation was measured. As a result, it was less than 3.0 at thewavelength 193 nm of ArF excimer laser exposure light and thus areduction in optical density was observed. Further, a section of alight-shielding film pattern was observed in detail using a TEM(transmission electron microscope). As a result, a modified layer asconventionally formed was confirmed and it was also confirmed that anincrease in line width (CD change) due to the modified layer was 15 nm.

The binary masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was confirmed in both cases.

Further, as a result of observing in detail a mask surface after theirradiation, deposits due to precipitation of Mo as conventionallyformed were confirmed on the transparent substrate (glass substrate) orthe film.

Example 8

FIG. 1 is a sectional view of a phase shift mask blank 10 of Example 8.

Using a synthetic quartz glass substrate having a 6-inch square sizewith a thickness of 0.25 inches as a transparent substrate 1, alight-semitransmitting film (MoSiNCH film) containing carbon andhydrogen in nitrided molybdenum and silicon was formed as a thin film 2on the transparent substrate 1.

Specifically, using a mixed target of molybdenum (Mo) and silicon (Si)(Mo:Si=10 mol %:90 mol %), reactive sputtering (DC sputtering) wascarried out by setting the power of a DC power supply to 3.0 kW in amixed gas atmosphere of argon (Ar), nitrogen (N₂), methane (CH₄), andhelium (He) (gas flow rate ratio Ar:N₂:CH₄:He=9:90:1:120) at a gaspressure of 0.3 Pa, thereby forming a MoSiNCH film made of molybdenum,silicon, nitrogen, carbon, and hydrogen and having a thickness of 69 nm.This MoSiNCH film had a transmittance of 6.11% and a phase difference of175.6 degrees at the wavelength 193 nm of ArF excimer laser exposurelight.

In the manner described above, the phase shift mask blank 10 of Example8 was manufactured.

Then, a halftone phase shift mask was manufactured using the phase shiftmask blank 10. FIG. 2 is sectional views showing processes ofmanufacturing the phase shift mask using the phase shift mask blank 10.

First, a chemically amplified positive resist film for electron beamwriting (PRL009 manufactured by FUJIFILM Electronic Materials Co., Ltd.)was formed as a resist film 3 on the mask blank 10 (see FIG. 2, (A)).The resist film 3 was formed by spin coating using a spinner (spincoating apparatus).

Then, using an electron beam writing apparatus, a required pattern waswritten on the resist film 3 formed on the mask blank 10 and,thereafter, the resist film 3 was developed with a predetermineddeveloper, thereby forming a resist pattern 3 a (see FIG. 2, (B) and(C)).

Then, using the resist pattern 3 a as a mask, the thin film 2 in theform of the light-semitransmitting film (MoSiNCH film) was etched,thereby forming a light-semitransmitting film pattern 2 a (see FIG. 2,(D)). A mixed gas of SF₆ and He was used as a dry etching gas.

Then, the remaining resist pattern was stripped, thereby obtaining aphase shift mask 20 (see FIG. 2, (E)). There was almost no change in thetransmittance and phase difference of the light-semitransmitting film ascompared with those at the time of the manufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained phaseshift mask so that the total dose became 30 kJ/cm². As described before,the dose of 30 kJ/cm² (energy density: about 25 mJ/cm²) corresponds tothe use of about 100,000 times of a photomask and corresponds to the usefor about three months with a normal frequency of use of a photomask.

The transmittance and phase difference of the light-semitransmittingfilm (MoSiNCH film) after the ArF excimer laser irradiation weremeasured. As a result, the transmittance was 6.70% and the phasedifference was 173.1 degrees for the ArF excimer laser. Therefore,changes before and after the irradiation were such that the change intransmittance was +0.59% and the change in phase difference was −2.5degrees, and thus, the changes were suppressed to be small and thechanges on this level do not affect the performance of the photomask.

Further, a section of the light-semitransmitting film pattern wasobserved in detail using a TEM (transmission electron microscope). As aresult, a thick modified layer as conventionally formed was notparticularly confirmed and, further, an increase in line width (CDchange) was suppressed to 15 nm or less. Therefore, it is seen that thephase shift mask blank and the phase shift mask of Example 8 haveextremely high irradiation durability to cumulative irradiation of anexposure light source with a short wavelength of 200 nm or less.

The phase shift masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was not confirmed in either case and thus thechemical resistance was excellent.

Further, as a result of observing in detail a mask surface after theirradiation, deposits due to precipitation of Mo as conventionallyformed were not particularly confirmed on the transparent substrate(glass substrate) or the film.

Comparative Example 2

Using a synthetic quartz glass substrate having a 6-inch square sizewith a thickness of 0.25 inches as a transparent substrate, alight-semitransmitting film (MoSiN film) made of nitrided molybdenum andsilicon was formed on the transparent substrate.

Specifically, using a mixed target of molybdenum Mo and silicon Si(Mo:Si=10 mol %:90 mol %), reactive sputtering (DC sputtering) wascarried out by setting the power of a DC power supply to 3.0 kW in amixed gas atmosphere of argon Ar, nitrogen N₂, and helium He (gas flowrate ratio Ar:N₂:He=5:49:46) at a gas pressure of 0.3 Pa, therebyforming a MoSiN film made of molybdenum, silicon, and nitrogen andhaving a thickness of 69 nm. This MoSiN film had a transmittance of6.11% and a phase difference of 175.6 degrees at the wavelength 193 nmof ArF excimer laser exposure light.

In the manner described above, a phase shift mask blank of ComparativeExample 2 was manufactured.

Then, a phase shift mask was manufactured using this phase shift maskblank in the same manner as in Example 8. There was almost no change inthe transmittance and phase difference of the light-semitransmittingfilm in the manufactured phase shift mask as compared with those at thetime of the manufacture of the mask blank.

An ArF excimer laser was continuously irradiated on the obtained phaseshift mask of Comparative Example 2 so that the total dose became 30kJ/cm². The transmittance and phase difference of thelight-semitransmitting film (MoSiN film) after the ArF excimer laserirradiation were measured. As a result, the transmittance was 7.69% andthe phase difference was 170.8 degrees for the ArF excimer laser.Therefore, changes before and after the irradiation were such that thechange in transmittance was +1.58% and the change in phase differencewas −4.8 degrees, and thus the changes were very large. If the changeson this level occur, the phase shift mask cannot be used any longer as aphotomask. Further, a section of a light-semitransmitting film patternwas observed in detail using a TEM (transmission electron microscope).As a result, a modified layer as conventionally formed was confirmed andit was also confirmed that an increase in line width (CD change) due tothe modified layer was 25 nm.

The phase shift masks were respectively immersed in an ammonia hydrogenperoxide mixture and in hot water in the same manner as in Example 1,thereby examining the chemical resistance thereof, particularly thechemical resistance (ammonia hydrogen peroxide mixture resistance, hotwater resistance) of pattern side walls. As a result, corrosion of thepattern side walls was confirmed in both cases.

Further, as a result of observing in detail a mask surface after the ArFexcimer laser irradiation, deposits due to precipitation of Mo asconventionally formed were confirmed on the transparent substrate (glasssubstrate) or the film.

DESCRIPTION OF SYMBOLS

-   -   1 transparent substrate    -   2 thin film    -   2′ modified layer    -   3 resist film    -   10 photomask blank    -   20 photomask

The invention claimed is:
 1. A photomask blank for use in manufacture ofa photomask adapted to be applied with exposure light having awavelength of 200 nm or less, comprising: a transparent substrate; and athin film on the transparent substrate; wherein the thin film is made ofa material containing a transition metal (M), silicon, and carbon andcomprising (i) a transition metal carbide or (ii) a silicon carbide anda transition metal carbide, and wherein the thin film contains M-C bondsand has a carbon content of 1-20 at %, the thin film being substantiallyfree of oxygen.
 2. The photomask blank according to claim 1, wherein thethin film is a light-semitransmitting film, and an atomic ratio of thetransition metal and the silicon is 1:1.5 to 1:24.
 3. The photomaskblank according to claim 1, wherein the thin film is a light-shieldingfilm, and an atomic ratio of the transition metal and the silicon is 1:1to 1:24.
 4. A method of manufacturing a photomask, comprising a step ofpatterning, by etching, the thin film in the photomask blank accordingto claim
 1. 5. A photomask manufactured by using the photomask blankaccording to claim
 1. 6. The photomask according to claim 5, wherein anincrease in a line width of a thin film pattern is 20 nm or less, whenan ArF excimer laser is continuously irradiated so that a total dosebecomes 30 kJ/cm².
 7. A method of manufacturing a semiconductor devicemanufactured by using the photomask according to claim
 5. 8. Thephotomask blank according to claim 1, wherein the thin film comprises aplurality of layers, at least one of the plurality of layers comprising(i) the transition metal carbide or (ii) the silicon carbide and thetransition metal carbide.
 9. A photomask blank manufacturing method foruse in manufacture of a photomask adapted to be applied with exposurelight having a wavelength of 200 nm or less, the method comprising astep of forming a thin film on a transparent substrate, wherein the thinfilm is formed by sputtering using a target containing carbon or anatmospheric gas containing carbon, the thin film containing a transitionmetal (M), silicon, and carbon and comprising (i) a transition metalcarbide or (ii) a silicon carbide and a transition metal carbide, andwherein the thin film contains M-C bonds and has a carbon content of1-20 at %, the thin film being substantially free of oxygen.
 10. Thephotomask blank manufacturing method according to claim 9, wherein thethin film is formed by adjusting pressure of the atmospheric gas and/orpower in the sputtering.
 11. The photomask blank manufacturing methodaccording to claim 9, wherein the thin film is formed so as to suppressan increase in a line width of a thin film pattern to 20 nm or less,when an ArF excimer laser is continuously irradiated on the manufacturedphotomask so that a total dose becomes 30 kJ/cm².
 12. The photomaskblank manufacturing method according to claim 9, wherein the thin filmis a light-semitransmitting film, and an atomic ratio of the transitionmetal and the silicon is 1:1.5 to 1:24.
 13. The photomask blankmanufacturing method according to claim 9, wherein the thin film is alight-shielding film, and an atomic ratio of the transition metal andthe silicon is 1:1 to 1:24.
 14. The photomask blank manufacturing methodaccording to claim 9, wherein the thin film is formed by adjusting atleast one of pressure of the atmospheric gas and power in the sputteringso as to form stable Si—C bonds and stable transition metal M-C bonds inthe thin film during the sputtering.
 15. The photomask blankmanufacturing method according to claim 9, wherein the thin filmcomprises a plurality of layers, at least one of the plurality of layerscomprising (i) the transition metal carbide or (ii) the silicon carbideand the transition metal carbide.